Technical Field
The present disclosure relates to a programmable logic controller (PLC) system, and, more particularly, a PLC system configured to perform backup of user data through an auxiliary power supply when power supply from a power module is interrupted.
Description of the Related Art
Previously, factory systems have been operated by individually controlling machines or apparatuses. However, modern industry becomes increasingly complicated and diversified, and thus such systems need to be changed accordingly. To support complicated systems and safely operate major facilities, additional apparatuses are required. As one of such apparatuses, a PLC system has been developed to directly control lines at industrial sites.
The PLC is an electronic device configured to use a programmable memory and control various types of machines or processors in order to perform special functions such as logic, sequencing, timing, counting, calculation, etc., through a digital or analog input/output module.
The PLC is usually the most fundamental controller along with the industry automation and is a system commonly utilized for the facility automation in a factory, a building or the like. At its early stage, the PLC system performed simple and basic calculations. Nowadays, the PLC system not only performs complicated application calculations but also forms an industrial network, thereby meeting various demands at the fields.
As shown in FIG. 1, a conventional PLC system 10 includes a single base 102, a power module 104, a Central Processing Unit (CPU) module 106, a communications module 108, an I/O module 110, and other modules 112. The base 102 may generally mount thereon the single power module 104 and the CPU module 106. Further, the base 102 may mount thereon the communications module 108, the I/O module 110 and the other modules 112 within a range of space where the base can allow them to be mounted. In addition, the single base 102 may mount thereon the single power module 104, meaning that the number of modules mounted on the bases 102 is limited depending on the power which can be supplied from the power module 104.
FIG. 2 illustrates a configuration of a CPU module included in the conventional PLC system.
The CPU module 106 included in the conventional PLC system is supplied with the power from the power module for the operation. A MCU (Micro Controller Unit) 208 included in the CPU module 106 performs control functions on another module as well as various calculation functions, and performs functions of managing user data. Such functions may be performed by the power supplied from the power module 104, whereby the supply of power from the power module 104 may be interrupted if abnormality occurs in the power module 104.
When the supply of power from the power module 104 is interrupted, the MCU 208 controls a switching unit 204 to substitute an auxiliary power supply 202 as a power supply source. Accordingly, the MCU 208 and a SRAM 206 are supplied with the power accumulated on the auxiliary power supply 202. The MCU 208 performs an operation of backing up the user data stored in the MCU 208 into the SRAM 206.
By the way, according to the conventional technology as shown in FIG. 2, a secondary battery such as a lithium-ion battery is usually employed as the auxiliary power supply 202. However, such a secondary battery has any problems that its charging period of time is long and its lifetime is short.
Further, while in the conventional technology as shown in FIG. 2, a low-speed memory such as a Static Random-Access Memory (SRAM) is used, a higher power is required for the operation of the memory when a high-speed memory such as a flash memory is used. However, the secondary battery such as the lithium-ion battery has any problem that it is difficult to provide the high-speed memory with a sufficient power for the operation due to the limitation of capacity.
In addition, the secondary battery may be likely to explode in the course of repeating a charging and a discharging thereof